The present invention relates to a steering device for a vehicle, especially for a motor vehicle, having an airbag module.
A conventional steering device for a vehicle that has an airbag module, especially for a motor vehicle, includes a steering column having an extreme steering-wheel hub, to which the steering wheel is mounted. The steering wheel hub is preferably designed to be cup-shaped and includes an outlet wall having an openable cover, behind which the airbag module is disposed. The airbag module includes a gas generator and an airbag. In the activated state of the airbag module, the cover unblocks an airbag outlet, through which the airbag can be inflated in front of the steering wheel.
The covers are specifically in the form of flaps and lids, which are broken at prenotched edge slots of a cover, by a triggered airbag and the pressure building up therein, and which swing into the interior of the vehicle. In order to prevent such lids from flying uncontrollably into the passenger compartment, catch bands may be used, which restrain the flaps or lids. This manner of opening valves by means of the airbag can undesirably hinder the inflation and unfolding operation, particularly in connection with flaps that are restrained by catch bands.
Steering devices are special designs constructed in a complicated manner, so that, for example, airbag modules which are developed for an instrument panel of a vehicle, as are described, for example, in German Published Patent Application Nos. 199 31 815, 299 12 825, 197 26 878, 197 50 182 and 197 33 896, and in which a tensile force is applied to an airbag-module cover by a pyrotechnically activatable cable line to unblock an airbag outlet, cannot easily be applied to steering devices. In the case of such airbag modules developed for an instrument panel of a vehicle, one must especially consider that, in the rearward direction, i.e. in the direction of the engine compartment, there is only a small space for displacing individual component parts. In addition, the design of a steering device requires that it be constructed in an extremely compact manner since, in contrast to an instrument panel, considerably less installation space is available.
It is an object of the present invention to provide a steering device for a vehicle, especially for a motor vehicle, having an airbag module, in which the steering device can be manufactured easily and inexpensively and in which it is possible to open the cover in the region of the steering-wheel hub, in a functionally reliable and rapid manner, in order to unblock the airbag outlet.
According to the present invention, the cover is connected to at least one pulling means, which can be actuated by a pyrotechnic actuator that is in the form of a cylinder-piston unit. In this cylinder-piston unit, the gas generator constitutes the piston, which is supported in a steering-wheel-hub cylinder region acting as a cylinder and/or steering-column cylinder region acting as a cylinder, so as to be moveable from a neutral position to a working position. The at least one pulling device is indirectly and/or directly connected to the gas generator in such a manner, that, in response to the gas generator being shifted in the cylinder region, a tensile force can be applied to the at least one pulling device so that the pulling device transfers the cover from its covering position into its open position for unblocking the airbag outlet.
Such a device may be manufactured easily and inexpensively, since the steering-device and airbag-module components and component parts required, namely the normally cylindrical wall region of the steering column and/or of the steering-wheel hub, used as the cylinder region, as well as the gas generator used as the piston, may also function to open the cover. Such an integration of functions in a steering device allows a necessary, compact method of construction to be easily implemented. In addition, the simple, preferably linear movement of the gas generator allows a simple design using longitudinal guide elements and permits the cover to be opened in a functionally reliable and rapid manner.
In one embodiment of the present invention, the at least one pulling device is formed by the airbag having at least one airbag-subsection fastened to the cover so that, in response to the gas generator being moved in the cylinder region, e.g., in the direction away from the cover, a tensile force may be applied to the at least one airbag-subsection. In this manner, the cover is transferred into its open position, e.g., into an area behind the outlet wall, and the airbag is subsequently inflated through the airbag outlet. Therefore, the airbag also functions to open the cover, whereby the number of component parts is advantageously reduced further, since separate pulling devices are not required for opening the cover. In addition, it is simple to manufacture an airbag folded in such a manner, so that, on the whole, such a design can be produced very inexpensively.
In an alternative embodiment of the present invention, the pulling device is formed by a cable line, which is guided over fixed deflection points, around the airbag module, to the cover so that, in response to the gas generator being moved in the cylinder region, e.g., in a direction away from the cover, a tensile force can be applied to the cable line, so that the tensile force transfers the cover into its open position, and the airbag subsequently exits through the airbag outlet, and can be inflated. Using such a design, the tensile force acting on the cover, and therefore the opening kinematics, may be adapted individually to the respective mounting situation, by the number, the type, and the size of the deflection points. In particular, the tensile force necessary to open the cover can be reduced by deflecting the cable line over several deflection pulleys. This arrangement allows the airbag module to be activated in a concerted and controlled manner and allows the cover to be opened in a functionally reliable and rapid manner.
In another embodiment of the present invention, a first, stationary deflection point is mounted at each of the two sides of a lower gas-generator end, so as to be set apart from the lower gas-generator end. A subsection of the cable line is guided around these first, stationary deflection points in such a manner, that this subsection runs approximately horizontally, and is preferably disposed directly adjacently to the lower gas-generator end. The first, stationary deflection points are set apart from each other so that the gas generator may be moved between and through these deflection points while pulling the cable line along. Such a design allows the cover to be opened rapidly, since a tensile force may already be applied immediately to the cable line, as the gas generator begins to move.
Another embodiment of the present invention provides for each of the first, stationary deflection points having a second, stationary deflection point assigned to it, which is shifted further to the outside, in relation to the lower gas-generator end, and is lower than the respective, first stationary deflection point. The second, stationary deflection points may be at the same level relative to the bottom end of the gas generator. The cable line extending from the first, stationary deflection points is then guided around the respective, second, stationary deflection points, and possibly over additional, stationary deflection points, in the direction of the cover. Such a design allows the cable to be guided in an advantageous manner, while a tensile force, which can be set precisely, acts on the cover.
The cable line may be guided upwardly by each of the free cable ends on the two sides of the airbag module, in the direction of the cover and may be secured in position in an edge area at the extremity. In response to the gas generator being shifted in a direction away from the cover, between and through the two first, stationary deflection points, while pulling the cable line along, a tensile force acts on the two cable ends so that they, together with respective subsections of the cover, may swivel outwardly, about a stationary, hinged bearing, in the direction of the outlet wall, in order to open the airbag outlet. Particularly in conjunction with a single-stage gas generator, this rapidly opens the airbag outlet for an airbag to exit through. Particularly in conjunction with a two-stage gas generator, in which the first stage is merely used to displace the gas generator, the cable ends may also be fastened to the cover so that they are swiveled inwardly, into the hub region. Then, the second stage is only triggered after the cover swings in.
In the neutral position, the airbag may be accommodated in a separate airbag cup, which is secured in position, near the steering-wheel hub and/or steering column, set apart from it. In this case, the cable line may be guided in the region between the airbag cup and a side of the steering-wheel hub and/or of the steering column, whereby the airbag is separated from the cable line, and they cannot interfere with each other.
In an additional embodiment of the present invention, the gas generator used as a piston and having a pre-chamber housing, which is in the form of a cylinder region, and is connected to the steering-wheel hub and/or steering column or integrally formed with it, is supported so as to be moveable in the direction of the cover. After being activated, the gas generator injects gas, via exhaust ports, into the prechamber housing, which is closed in a gas-tight manner, and is opposite to the cover, and the gas generator builds up a displacement pressure for moving the gas generator into the working position. Using such a design, the gas generator, and therefore the airbag, is already moved in the airbag-outlet direction, i.e., in the unfolding and inflation direction, at the start of the activation. This movement in the direction of the cover is simultaneously used to open the cover.
The at least one pulling device is connected to the gas generator, via a pulling-direction deflector, so that the cover can be moved behind the outlet wall by the gas generator, in a direction that is approximately opposite to that of the gas generator, which can move in the direction of the cover.
In still another embodiment of the present invention, the airbag can only be inflated in the shifted working position of the gas generator, via a gas connection, in response to the gas generator being activated. This arrangement achieves a high opening reliability, since, after the gas generator is activated, the escaping gas is initially used for moving the gas generator only, in order to open the cover. Then, the gas that continues to escape is only subsequently used to inflate the airbag, after a time delay, in the case of an already open airbag outlet.
In one embodiment of the present invention, at least one overflow opening may be positioned at the prechamber housing, in the sliding path of the gas generator, e.g., near the shifted working position of the gas generator, the overflow opening producing a gas connection to the airbag after the gas generator travels past the overflow opening. Therefore, prior to the overflow opening being reached, there is still no gas connection between the gas generator and the airbag, so that, after its activation, the gas generator is initially only used as an actuator for reliably opening the cover, and only subsequently used to inflate the airbag.
The gas generator may include radial blow-off outlets, the moveable gas generator and the moveable airbag module being guided along the displacement path in a gas-tight manner, in the pre-chamber housing, by at least one sealing element. This arrangement achieves a high functional reliability of the opening actuator.
Rods or tension members may also be used as tension elements. It may be particularly advantageous and inexpensive to provide a cable line as the at least one pulling device, which, starting out from the gas generator, is guided out of the prechamber housing in a gas-tight manner, in the direction opposite to the movement of the gas generator, and over at least two stationary deflection points, around the prechamber housing, to the cover located in front of the prechamber housing, at a distance from it. The cable line is connected there. The engaging movement of the gas generator may deflect the cable line from the original position, in order to generate the opening force for the cover.
A one-stage gas generator may be used as a gas generator, which may be shifted due to the recoiling caused by the discharging gas. However, one embodiment of the present invention provides for the gas generator being a two-stage gas generator, the pyrotechnic actuator being operable in the first generator stage, after the gas generator is activated by a crash sensor, and the airbag being inflatable in the second generator stage, after a time delay.
The cover may be formed by at least one openable airbag flap, which can swivel in or out to the airbag module, the cover being designed to selectively break, and therefore, to selectively open the airbag outlet, using an outer skin that can break at a notch.
An additional safety function results from the fact that a subsection in the region of the steering-wheel hub and/or steering column is designed as a deformation region. For example, such a deformation region may be designed to have an undulated profile and/or to be a type of inverted tube.